Author Identifier
Date of Award
2026
Keywords
myrtle rust, biosecurity, host susceptibility, disease surveillance, provenance variation, plant phenology
Document Type
Thesis
Publisher
Edith Cowan University
Degree Name
Doctor of Philosophy
School
School of Science
First Supervisor
Anna Hopkins 
0000-0001-8090-5544
Second Supervisor
Kristina Lemson 0000-0002-8342-9528
Third Supervisor
Mary Hanson 0000-0001-6028-5691
Fourth Supervisor
Kylie Ireland
Abstract
Myrtle rust (Austropuccinia psidii) is a potential emerging threat to biodiversity and plant industries in Western Australia (WA). Since its arrival in Australia in 2010, the pathogen has caused widespread ecological damage along the east coast, infecting more than 375 species. In June 2022, A. psidii was detected for the first time in WA, on Melaleuca species in the Eastern Kimberley. This incursion has heightened concerns regarding the pathogen’s potential impact on WA’s myrtaceous flora, particularly in the south-west biodiversity hotspot, where Myrtaceae dominate native vegetation and urban forests. This thesis addressed critical aspects of WA’s vulnerability to A. psidii through complementary lines of investigation. First, in Chapter 2, urban forest risk was assessed using tree inventory data from selected Local Government Areas (LGAs) in Perth. Myrtaceae were found to comprise 45.2 % to 60.7 % of street trees, with highly susceptible species widespread across the city. GIS-based mapping and scenario modelling indicated that under conducive climatic conditions, a myrtle rust incursion could cause substantial loss of urban canopy cover, significantly altering Perth’s street tree estate.
In Chapter 3, susceptibility screening was undertaken using artificial inoculations of 13 species native to south-west WA. Responses varied among species, with most species showing some level of infection. Overall, the proportion of susceptible seedlings (disease severity categories 3 – 5) ranged from 50 % to 100 % among species. The highest susceptibility was recorded in Taxandria spathulata and Eremaea pauciflora, where 100 % of seedlings were susceptible, followed by Agonis baxteri (93.7 %), Eremaea purpurea (90.0 %) and Beaufortia purpurea (87.5 %). These findings highlight species at greatest risk and emphasise the need for targeted conservation strategies.
Agonis flexuosa is an iconic species, endemic to WA and widely planted as an amenity tree. In Chapter 4, provenance trials of Ag. flexuosa demonstrated significant variation in susceptibility across 13 provenances, with responses ranging from high resistance to moderate susceptibility. In addition, phenological assessment identified potential periods of heightened infection risk, particularly during early autumn and spring, extending into early summer. Together, these results indicate underlying genetic and phenological drivers of disease risk, suggesting that Ag. flexuosa may be vulnerable to myrtle rust during future incursions in the south-west of WA. This highlights the need for broader genetic analyses across the species’ native range and underscores the need for species conservation measures that maintain genetic diversity, safeguard potentially resistant genotypes, and preserve adaptive variation within natural populations.
Finally, in Chapter 5, surveys of Ag. flexuosa in the Perth metropolitan area and Torndirrup National Park identified Neofusicoccum australe as a common foliar pathogen. Confirmation of its pathogenicity provides a baseline for distinguishing non-threatening foliar symptoms from those caused by A. psidii and provides a valuable resource for myrtle rust surveillance.
Collectively, this research demonstrates that both natural ecosystems and urban forests in WA are highly vulnerable to A. psidii. It advances understanding of host susceptibility, highlights the interaction of host distribution and climate in shaping risk and identifies key priorities for surveillance and conservation planning. Strengthening preparedness through host screening, genetic studies and monitoring in high-risk environments is essential to mitigate the potential ecological and cultural impacts of myrtle rust should further incursions occur in WA.
Access Note
Access to this thesis is embargoed until 10th October 2031
Recommended Citation
Asare, E. K. (2026). Austropuccinia psidii in south-west Western Australia: Understanding its potential impact through epidemiology and host responses. Edith Cowan University. https://doi.org/10.25958/srex-e641